Refrigerated semitrailer truck for long and local deliveries

Abstract

A refrigerated semitrailer truck for both long and local delivery of frozen foods in a hot environment is disclosed which utilizes both a liquid nitrogen unit and a mechanical refrigeration unit with an automatic control system. The system automatically turns the liquid nitrogen off when the temperature is above 30° F., below -10° F., or when an access door to the insulated truck is open. The liquid nitrogen also operates as a standby unit at all temperatures above -10° F. in the event of a malfunction of the mechanical unit.

What is claimed is: 
     
       1. A vehicle for transporting a substantial load of frozen foods over a substantial distance and then off-loading portions of the load at each of a number of relatively closely spaced destinations which comprises: a vehicle having an insulated load carrying compartment having at least one access door;   a mechanical refrigeration unit for refrigerating the compartment by means of a compression-expansion refrigeration cycle;   a cryogenic refrigeration unit for introducing liquified gas into the compartment when enabled by a manual switch of a control system and not disabled by the control system; and   a control system including a. manual means for manually enabling operation of the control system,   b. high temperature means for automatically disabling the cryogenic refrigeration unit in response to the temperature of the air space in the compartment rising above a predetermined maximum value,   c. detection means for disabling the high temperature means to permit operation of the cryogenic refrigeration unit in response to a failure of the compression-expansion refrigerator unit to maintain the temperature of the air space in the chamber at or below the predetermined maximum value,   d. low temperature means for disabling the cryogenic refrigeration unit in response to the temperature of the air space compartment falling below a predetermined minimum value, and   e. door detection means for automatically disabling the cryogenic refrigeration unit when an access door to the compartment is opened.     
     
     
       2. A vehiclefor transporting a substantial load of frozen foods over a substantial distance and then off-loading portions of the load at each of a number of relatively closely spaced destinations which comprises: a vehicle having an insulated load carrying compartment having at least one access door;   a mechanical refrigeration unit for refrigerating the compartment by means of a compression-expansion refrigeration cycle;   a cryogenic refrigeration unit for introducing liquified gas into the compartment when enabled by a manual switch of a control system and not disabled by the control system; and   a control system including a. manual means for manually enabling operation of the cryogenic refrigeration unit,   b. high temperature means for automatically disabling the cryogenic refrigeration unit in response to the temperature of the air space in the compartment rising above a predetermined maximum value,   c. low temperature means for disabling the cryogenic refrigeration unit in response to the temperature of the air space compartment falling below a predetermined minimum value, and   d. door detection means for automatically disabling the cryogenic refrigeration unit when an access door to the compartment is opened.     
     
     
       3. A vehicle for transporting a substantial load of frozen foods over a substantial distance and then off-loading portions of the load at each of a number of relatively closely spaced destinations which comprises: a vehicle having an insulated load carrying compartment having at least one access door;   a mechanical refrigeration unit for refrigerating the compartment by means of a compression-expansion refrigeration cycle;   a cryogenic refrigeration unit for introducing liquified gas into the compartment when enabled by a manual switch of a control system and not disabled by the control system; and   a control system including a. manual means for manually enabling operation of the cryogenic refrigeration unit,   b. low temperature means for disabling the cryogenic refrigeration unit in response to the temperature of the air space compartment falling below a predetermined minimum value, and   c. door detection means for automatically disabling the cryogenic refrigeration unit when an access door to the compartment is opened.     
     
     
       4. A vehicle for transporting a substantial load of frozen foods over a substantial distance and then off-loading portions of the load at each of a number of relatively closely spaced distinations which comprises: a vehicle including a semitrailer having an insulated load carrying compartment having at least one access door;   a mechanical refrigeration unit for refrigerating the compartment by means of a compression-expansion refrigeration cycle, said refrigerating unit including an internal combustion engine which drives a compressor;   a cryogenic refrigeration unit for introducing liquified gas into the compartment when enabled by a manual switch of a control system and not disabled by the control system; and   a control system including a. manual means for manually enabling operation of a cryogenic refrigeration unit,   b. high temperature means for automatically disabling the cryogenic refrigeration unit in response to the temperature of the air space in the compartment rising above a predetermined maximum value,   c. detection means for disabling the high temperature means in response to a failure of the compression-expansion refrigerator unit to maintain operation of the cryogenic refrigeration unit when the air space in the chamber is above the predetermined maximum value, including means responsive to termination of operation of the internal combustion engine,   d. low temperature means for disabling the cryogenic refrigeration unit in response to the temperature of the air space compartment falling below a predetermined minimum value, and   e. door detection means for automatically disabling the cryogenic refrigeration unit when an access door to the compartment is opened.     
     
     
       5. A vehicle for transporting a substantial load of frozen foods over a substantial distance and then off-loading portions of the load at each of a number of relatively closely spaced destinations which comprises: a vehicle having an insulated load carrying compartment having at least one access door;   a mechanical refrigeration unit for refrigerating the compartment by means of a compression-expansion refrigeration cycle;   a cryogenic refrigeration unit for introducing liquified gas into the compartment when enabled by a manual switch of a control system and not disabled by the control system; and   a control system including a manual means for manually enabling operation of the cryogenic refrigeration unit, and   b. low temperature means for disabling the cryogenic refrigeration unit in response to the temperature of the air space compartment falling below a predetermined minimum value.     
     
     
       6. A vehicle for transporting a substantial load of frozen foods over a substantial distance and then off-loading portions of the load at each of a number of relatively closely spaced destinations which comprises: a vehicle having an insulated load carrying compartment having at least one access door;   a mechanical refrigeration unit for refrigerating the compartment by means of a compression-expansion refrigeration cycle;   a cryogenic refrigeration unit for introducing liquified gas into the compartment when enabled by a manual switch of a control system and not disabled by the control system; and   a control system including a manual means for manually enabling operation of the control system,   b. means for automatically enabling operation of the cryogenic refrigeration unit in response to detecting a failure of the compression-expansion refrigeration unit, and   c. low temperature means for disabling the cryogenic refrigeration unit in response to the temperature of the air space compartment falling below a predetermined minimum value.